gcc/ada/contracts.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                            C O N T R A C T S                             --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2015-2023, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 --  This package contains routines that perform analysis and expansion of
  27 --  various contracts.
  28
  29 with Types; use Types;
  30
  31 package Contracts is
  32
  33    procedure Add_Contract_Item (Prag : Node_Id; Id : Entity_Id);
  34    --  Add pragma Prag to the contract of a constant, entry, entry family,
  35    --  [generic] package, package body, protected unit, [generic] subprogram,
  36    --  subprogram body, variable, task unit, or type denoted by Id.
  37    --  The following are valid pragmas:
  38    --
  39    --    Abstract_State
  40    --    Always_Terminates
  41    --    Async_Readers
  42    --    Async_Writers
  43    --    Attach_Handler
  44    --    Constant_After_Elaboration
  45    --    Contract_Cases
  46    --    Depends
  47    --    Effective_Reads
  48    --    Effective_Writes
  49    --    Exceptional_Cases
  50    --    Extensions_Visible
  51    --    Global
  52    --    Initial_Condition
  53    --    Initializes
  54    --    Interrupt_Handler
  55    --    No_Caching
  56    --    Part_Of
  57    --    Postcondition
  58    --    Precondition
  59    --    Refined_Depends
  60    --    Refined_Global
  61    --    Refined_Post
  62    --    Refined_States
  63    --    Subprogram_Variant
  64    --    Test_Case
  65    --    Volatile_Function
  66
  67    procedure Analyze_Contracts (L : List_Id);
  68    --  Analyze the contracts of all eligible constructs found in list L
  69
  70    procedure Analyze_Pragmas_In_Declarations (Body_Id : Entity_Id);
  71    --  Perform early analysis of pragmas at the top of a given subprogram's
  72    --  declarations.
  73    --
  74    --  The purpose of this is to analyze contract-related pragmas for later
  75    --  processing, but also to handle other such pragmas before these
  76    --  declarations get moved to an internal wrapper as part of contract
  77    --  expansion. For example, pragmas Inline, Ghost, Volatile all need to
  78    --  apply directly to the subprogram and not be moved to a wrapper.
  79
  80    procedure Analyze_Entry_Or_Subprogram_Body_Contract (Body_Id : Entity_Id);
  81    --  Analyze all delayed pragmas chained on the contract of entry or
  82    --  subprogram body Body_Id as if they appeared at the end of a declarative
  83    --  region. Pragmas in question are:
  84    --
  85    --    Always_Terminates  (stand alone subprogram body)
  86    --    Contract_Cases     (stand alone subprogram body)
  87    --    Depends            (stand alone subprogram body)
  88    --    Exceptional_Cases  (stand alone subprogram body)
  89    --    Global             (stand alone subprogram body)
  90    --    Postcondition      (stand alone subprogram body)
  91    --    Precondition       (stand alone subprogram body)
  92    --    Refined_Depends
  93    --    Refined_Global
  94    --    Refined_Post
  95    --    Subprogram_Variant (stand alone subprogram body)
  96    --    Test_Case          (stand alone subprogram body)
  97
  98    procedure Analyze_Entry_Or_Subprogram_Contract
  99      (Subp_Id   : Entity_Id;
 100       Freeze_Id : Entity_Id := Empty);
 101    --  Analyze all delayed pragmas chained on the contract of entry or
 102    --  subprogram Subp_Id as if they appeared at the end of a declarative
 103    --  region. The pragmas in question are:
 104    --
 105    --    Always_Terminates
 106    --    Contract_Cases
 107    --    Depends
 108    --    Exceptional_Cases
 109    --    Global
 110    --    Postcondition
 111    --    Precondition
 112    --    Subprogram_Variant
 113    --    Test_Case
 114    --
 115    --  Freeze_Id is the entity of a [generic] package body or a [generic]
 116    --  subprogram body which "freezes" the contract of Subp_Id.
 117
 118    procedure Analyze_Object_Contract
 119      (Obj_Id    : Entity_Id;
 120       Freeze_Id : Entity_Id := Empty);
 121    --  Analyze all delayed pragmas chained on the contract of object Obj_Id as
 122    --  if they appeared at the end of the declarative region. The pragmas to be
 123    --  considered are:
 124    --
 125    --    Async_Readers
 126    --    Async_Writers
 127    --    Depends           (single concurrent object)
 128    --    Effective_Reads
 129    --    Effective_Writes
 130    --    Global            (single concurrent object)
 131    --    Part_Of
 132    --
 133    --  Freeze_Id is the entity of a [generic] package body or a [generic]
 134    --  subprogram body which "freezes" the contract of Obj_Id.
 135
 136    procedure Analyze_Type_Contract (Type_Id : Entity_Id);
 137    --  Analyze all delayed pragmas chained on the contract of object Obj_Id as
 138    --  if they appeared at the end of the declarative region. The pragmas to be
 139    --  considered are:
 140    --
 141    --    Async_Readers
 142    --    Async_Writers
 143    --    Effective_Reads
 144    --    Effective_Writes
 145    --    Postcondition
 146    --    Precondition
 147    --
 148    --  In the case of a protected or task type, there will also be
 149    --  a call to Analyze_Protected_Contract or Analyze_Task_Contract.
 150
 151    procedure Analyze_Package_Body_Contract
 152      (Body_Id   : Entity_Id;
 153       Freeze_Id : Entity_Id := Empty);
 154    --  Analyze all delayed pragmas chained on the contract of package body
 155    --  Body_Id as if they appeared at the end of a declarative region. The
 156    --  pragmas that are considered are:
 157    --
 158    --    Refined_State
 159    --
 160    --  Freeze_Id is the entity of a [generic] package body or a [generic]
 161    --  subprogram body which "freezes" the contract of Body_Id.
 162
 163    procedure Analyze_Package_Contract (Pack_Id : Entity_Id);
 164    --  Analyze all delayed pragmas chained on the contract of package Pack_Id
 165    --  as if they appeared at the end of a declarative region. The pragmas
 166    --  that are considered are:
 167    --
 168    --    Initial_Condition
 169    --    Initializes
 170
 171    procedure Analyze_Protected_Contract (Prot_Id : Entity_Id);
 172    --  Analyze all delayed pragmas chained on the contract of protected unit
 173    --  Prot_Id if they appeared at the end of a declarative region. Currently
 174    --  there are no such pragmas.
 175
 176    procedure Analyze_Subprogram_Body_Stub_Contract (Stub_Id : Entity_Id);
 177    --  Analyze all delayed pragmas chained on the contract of subprogram body
 178    --  stub Stub_Id as if they appeared at the end of a declarative region. The
 179    --  pragmas in question are:
 180    --
 181    --    Always_Terminates
 182    --    Contract_Cases
 183    --    Depends
 184    --    Exceptional_Cases
 185    --    Global
 186    --    Postcondition
 187    --    Precondition
 188    --    Refined_Depends
 189    --    Refined_Global
 190    --    Refined_Post
 191    --    Subprogram_Variant
 192    --    Test_Case
 193
 194    procedure Analyze_Task_Contract (Task_Id : Entity_Id);
 195    --  Analyze all delayed pragmas chained on the contract of task unit Task_Id
 196    --  as if they appeared at the end of a declarative region. The pragmas in
 197    --  question are:
 198    --
 199    --    Depends
 200    --    Global
 201
 202    procedure Build_Entry_Contract_Wrapper (E : Entity_Id; Decl : Node_Id);
 203    --  Build the body of a wrapper procedure for an entry or entry family that
 204    --  has contract cases, preconditions, or postconditions, and add it to the
 205    --  freeze actions of the related synchronized type.
 206    --
 207    --  The body first verifies the preconditions and case guards of the
 208    --  contract cases, then invokes the entry [family], and finally verifies
 209    --  the postconditions and the consequences of the contract cases. E denotes
 210    --  the entry family. Decl denotes the declaration of the enclosing
 211    --  synchronized type.
 212
 213    procedure Create_Generic_Contract (Unit : Node_Id);
 214    --  Create a contract node for a generic package, generic subprogram, or a
 215    --  generic body denoted by Unit by collecting all source contract-related
 216    --  pragmas in the contract of the unit.
 217
 218    procedure Freeze_Previous_Contracts (Body_Decl : Node_Id);
 219    --  Freeze the contracts of all source constructs found in the declarative
 220    --  list which contains entry, package, protected, subprogram, or task body
 221    --  denoted by Body_Decl. In addition, freeze the contract of the nearest
 222    --  enclosing package body.
 223
 224    procedure Inherit_Subprogram_Contract
 225      (Subp      : Entity_Id;
 226       From_Subp : Entity_Id);
 227    --  Inherit relevant contract items from source subprogram From_Subp. Subp
 228    --  denotes the destination subprogram. The inherited items are:
 229    --    Extensions_Visible
 230    --  ??? it would be nice if this routine handles Pre'Class and Post'Class
 231
 232    procedure Instantiate_Subprogram_Contract (Templ : Node_Id; L : List_Id);
 233    --  Instantiate all source pragmas found in the contract of the generic
 234    --  subprogram declaration template denoted by Templ. The instantiated
 235    --  pragmas are added to list L.
 236
 237    procedure Make_Class_Precondition_Subps
 238      (Subp_Id         : Entity_Id;
 239       Late_Overriding : Boolean := False);
 240    --  Build helpers that at run time evaluate statically and dynamically the
 241    --  class-wide preconditions of Subp_Id; build also the indirect-call
 242    --  wrapper (ICW) required to check class-wide preconditions when the
 243    --  subprogram is invoked through an access-to-subprogram, or when it
 244    --  overrides an inherited class-wide precondition (see AI12-0195-1).
 245    --  Late_Overriding enables special handling required for late-overriding
 246    --  subprograms.
 247    --
 248    --  For example, if we have a subprogram with the following profile:
 249    --
 250    --     procedure Prim (Obj : TagTyp; <additional formals>)
 251    --       with Pre'Class => F1 (Obj) and F2(Obj)
 252    --
 253    --  We build the following helper that evaluates statically the class-wide
 254    --  precondition:
 255    --
 256    --    function PrimSP (Obj : TagTyp) return Boolean is
 257    --    begin
 258    --       return F1 (Obj) and F2(Obj);
 259    --    end PrimSP;
 260    --
 261    --   ... and the following helper that evaluates dynamically the class-wide
 262    --   precondition:
 263    --
 264    --    function PrimDP (Obj : TagTyp'Class; ...) return Boolean is
 265    --    begin
 266    --       return F1 (Obj) and F2(Obj);
 267    --    end PrimSP;
 268    --
 269    --   ... and the following indirect-call wrapper (ICW) that is used by the
 270    --   code generated by the compiler for indirect calls:
 271    --
 272    --    procedure PrimICW (Obj : TagTyp; <additional formals> is
 273    --    begin
 274    --       if not PrimSP (Obj) then
 275    --          $raise_assert_failure ("failed precondition in call at ...");
 276    --       end if;
 277    --
 278    --       Prim (Obj, ...);
 279    --    end Prim;
 280
 281    procedure Merge_Class_Conditions (Spec_Id : Entity_Id);
 282    --  Merge and preanalyze all class-wide conditions of Spec_Id (class-wide
 283    --  preconditions merged with operator or-else; class-wide postconditions
 284    --  merged with operator and-then). Ignored pre/postconditions are also
 285    --  merged since, although they are not required to generate code, their
 286    --  preanalysis is required to perform semantic checks. Resulting merged
 287    --  expressions are later installed by the expander in helper subprograms
 288    --  which are invoked from the caller side; they are also used to build
 289    --  the dispatch-table wrapper (DTW), if required.
 290
 291    procedure Preanalyze_Class_Conditions (Spec_Id : Entity_Id);
 292    --  Preanalyze class-wide pre-/postconditions of the given subprogram
 293    --  specification.
 294
 295    procedure Process_Class_Conditions_At_Freeze_Point (Typ : Entity_Id);
 296    --  Merge, preanalyze, and check class-wide pre/postconditions of Typ
 297    --  primitives.
 298
 299    procedure Save_Global_References_In_Contract
 300      (Templ  : Node_Id;
 301       Gen_Id : Entity_Id);
 302    --  Save all global references found within the aspect specifications and
 303    --  the contract-related source pragmas assocated with generic template
 304    --  Templ. Gen_Id denotes the entity of the analyzed generic copy.
 305
 306 end Contracts;